Silicone rubbers are used in a wide variety of fields, for example, health care materials such as bottle teats and food-safe goods, hoses and gasket materials for automobile use, building members, and fiber coating materials because of heat resistance, freeze resistance, safety, appearance (transparency), touch, and durability.
Silicone rubbers used as O-rings and gaskets are required to have a low compression set for preventing seal leakage. Typical silicone rubbers, however, have a substantial compression set and suffer from the problem of rubber shape change during long-term service in high-temperature applications. In order to reduce the compression set, often the rubbers shaped by heat curing must be further subject to secondary vulcanization at high temperature for a long time.
To solve the problem, Patent Document 1: JP-A H02-242854 proposes to add a triazole compound to an addition-curable silicone rubber composition for reducing the compression set thereof without a need for secondary vulcanization. However, the addition of a triazole compound to the silicone rubber composition gives rise to the problem that the cure rate is decelerated.